1. Field of the Invention
The present invention relates to microprocessor based devices operable while being held in a user's hand, such as a handheld computer. More particularly, the present invention pertains to handheld computing devices such as a personal digital assistant (PDA). The invention provides a foldable, pocket sized keyboard useful for such PDA's.
2. Description of the Related Art
Portable computing and communication devices are quickly becoming ubiquitous tools for both business and personal activities. The smallest and lightest of these devices are suitable for and most often carried and operated while being held in the hand of its user.
Portable data processing devices that assist with processing and information needs include calculators, organizers, personal digital assistants (PDAs), and notebook/laptop computers. Calculators are, of course, limited to mathematical operations. Organizers are able to receive information, store, process, and display certain types of alphanumeric information. Typically, they are used for keeping track of appointments and the like. Organizers differ from calculators in that they handle text information. Physically, organizers they are small enough to fit in a pocket or purse. While organizers can be thought of as computers, they hold a separate niche in the market because of their small size and the collection of special software packages employable, including a special operating system. An operating system is a set of fixed programs that control the general operation of the organizer, including the manner of interaction with the user. PDA's are small devices, typically smaller than a notebook computer, which store personal information and also may serve as an interface to communications. They typically include a means for data input; data processing means; display; and optionally telecommunications capabilities. PDAs, which are much more versatile computers, are often characterized by a relatively large touch sensitive screen which serves as both the input and output interface. PDA's have a unique operating system that accomplishes most calculating and data storage tasks by guiding the user through a sequence of selections. Typically, the operating system also includes an application for character recognition of script writing.
PDA's commonly have touch sensitive displays, or pressure sensitive screens such as are used in pen based computers. Such a display or screen offers a graphical user interface that allows the user to invoke and direct the information processing capabilities of the PDA and to input information by a simulated keypad. When the keypad is simulated, an image of a numerical keypad or alphabetical typewriter key layout appears on the screen. In these modes, a touch on the screen by a finger or a hard object such as a stylus, at the image of a key or button, results in the corresponding number or letter being input to the PDA. This approach has the disadvantage that the touch-sensitive screen feels unfamiliar to a user accustomed to using a mechanical keypad, so that the user is likely to make mistakes if entering data quickly. Whereas historically user input to computing and communication devices has been primarily through a keyboard, pen computers and PDAs have eliminated the keyboard, not only because its size and weight often make it inconvenient and impracticable to carry and use, but also because many mobile tasks require a more limited extent of textual input. As experience with these devices has increased, however, it has been recognized that from time to time nearly all applications and users would benefit from the ability to perform keyboard input. The tactile familiarity of the keypad increases the flexibility and ease of use of the device. Some PDAs do include a socket to connect to the cable from a conventional keyboard, however, such keyboards are large devices which are impractical to be portable. Attempts to incorporate keyboards with PDA's invariably produce units that are large, heavy, expensive, complex and difficult and cumbersome to transform from keyboard input to keyboardless operation. However, given the inconvenience of carrying, connecting and operating a completely external keyboard, PDA users almost universally elect to go without keyboard input even in those relative frequently occurring situations in which it would be beneficial.
What is needed is a PDA having a keyboard which is truly portable. It is, therefore, an object of the present invention to provide a device that permits the inclusion of a keyboard with a handheld computer. The present invention provides an improved PDA arrangement wherein data input is facilitated through a foldable, pocket sized keyboard which is conveniently portable together with the PDA. Foldable keyboards are known in the art. For example, foldable keyboards are known from U.S. Pat. No. 5,278,779; U.S. Pat. Nos. Des. 388,456; 5,653,543; 5,574,481; 5,457,453; 5,410,333; 5,267,127; 4,939,514; and 3,940,758. U.S. Pat. Des. 310,093 shows a folding calculator having a keyboard portion and a photocell portion. Such do not pertain to a portable, folding keyboard attachable to a PDA.